1. The Field of the Invention
The present invention relates generally to the treatment of waste such as agricultural and livestock waste. More specifically, the present invention relates to the separation of valuable components, such as nutrients and purified water, from waste, such as agricultural and livestock waste, by a process that includes controlled freezing and thawing, and by a system that includes the devices to achieve the same.
2. Relevant Technology
Feedlots, animal barns, agroindustrial plants, municipal sewage, and farms that keep large numbers of animals are sources of enormous quantities of organic waste. The expression xe2x80x9corganic waste sourcexe2x80x9d will hereinafter refer to any of these sources of organic waste or to any source that similarly produces organic waste, although perhaps in different quantities or by different activities. Accordingly, xe2x80x9corganic waste sourcexe2x80x9d will hereinafter also refer to organic waste recycling and treatment plants that produce liquid and/or sludge from which purified water can be separated.
The disposal of untreated organic waste causes serious pollution problems which include those due to the waste""s high content of chemically oxidizable components (expressed as COD, or chemical oxygen demand) and biochemically decomposable components (expressed as BOD, or biochemical oxygen demand). When these pollutants reach bodies of water, either because they leach from disposal sites or as a consequence of being directly released or transported into water bodies, they deoxygenate the receiving waters and impair the receiving waters"" capability to support aquatic life.
Acridity and high pathogen content add to the COD and BOD problems of untreated waste disposal. Acrid gases released into the atmosphere are not only unpleasant but they can also contribute to acid deposition, global greenhouse effects, and ozone depletion.
According to background material provided by the US Environmental Protection Agency (EPA), xe2x80x9canimal waste, if not managed properly, can run off farms and pollute nearby water bodies. Agricultural run off, rich in nutrients like nitrogen and phosphorous has been linked to dangerous toxic microorganisms such as Pfisteria piscicida. Pfisteria is widely believed to be responsible for major fish kills and disease events in several mid-Atlantic states and may pose a risk to human health.xe2x80x9d Draft Strategy for Animal Feeding Operations, EPA Memorandum, Mar. 4, 1998. See also EPA To Better Protect Public Health and The Environment From Animal Feeding Operations, EPA release of Mar. 5, 1998. In particular, the relationship between swine production and waste management problems has been reported in the Task Force Report No. 124, Council for Agricultural Science and Technology, Waste Management and Utilization in Food Production and Processing, October 1995, pp. 42-54, 110-121.
Notwithstanding the problems referred to above and other detrimental effects of the disposal of untreated organic waste, organic waste has nutritional value for plants and some forms of organic waste contain large quantities of water that could be recycled in purified, re-useable form. Land application of these dilute wastes is facing increased regulatory scrutiny. Furthermore, water in organic waste is highly polluted and it typically cannot be re-used directly even in agricultural and livestock operations. The alternative use of synthetic fertilizers is often adopted for increasing crop yield, but this solution carries at least two undesirable implications. First, a strategy that relies only on the use of synthetic fertilizers neglects the problem of organic waste disposal. Second, the manufacture of synthetic fertilizers frequently requires consumption of considerable amounts of energy and possibly expensive synthesis materials, sometimes involves polluting subprocesses, and may produce additional waste whose safe disposal is often expensive. In addition, the fast release of most synthetic fertilizers causes leaching, which in turn leads to wasted fertilizer and the ensuing pollution problems when the leached fertilizer accumulates in canals and other bodies of water. In addition to the foregoing two problems, polices that consider organic waste as an untreatable material neglect the recovery of the large quantities of water discarded with such waste, even though water is becoming a valuable and scarce resource.
The problems inherent to organic waste production and subsequent treatment require economical processes which avoid the afore-mentioned environmental problems. The efficiency of these processes is considerably enhanced when, in addition to providing a practical disposal of organic waste, the processes convert the organic waste into a useful product, such as commercial fertilizer, preferably a slow-release fertilizer and/or lead to the recovery of purified water that can be re-used in at least agricultural and/or livestock operations. This conversion requires the recovery of the nitrogenous products in the waste and their conversion into a fertilizer that can slowly release nitrogen in a form that plants can absorb. Because of the diversity of variables that determine the economic, chemical, and environmental aspects of this conversion problem, a variety of attempts to treat organic waste have been undertaken.
As indicated above, water is becoming a valuable and scarce resource to the extent that the availability of usable water limits municipal, industrial, and agricultural development in many areas. Methods for separating purified water from contaminated aqueous media have been disclosed.
These methods include the complete freezing and complete thawing of aqueous sludge to change the coagulation characteristics of the sludge for the purpose of achieving a subsequent more dense coagulation. Other methods rely on a combination of freezing with a mechanical treatment for separating precipitated material by complete freezing of the feed material followed by partial thawing and subsequent filtration or centrifugation. Some processes operate with contaminated feed that is mixed with immiscible refrigerant. Still other methods comprise the reduction of solid waste particles to atomizable size, the subsequent complete freezing of sprayed feed in a freezing chamber, and an eventual separation that requires the waste in permanent solid form. A number of methods rely on vacuum freezing with separation of low pressure water vapor and ice, or on solid-liquid-vapor multiple phase transformations. A variety of processes are designed so that a purified water component in contaminated water is frozen out in a freezer that relies on a conventional heat exchanger. Finally other methods rely on complete freezing followed by separation of volatile components and freeze-drying of the residue.
Natural freezing has been used in the purification of water produced in association with oil and natural gas production. This type of water typically contains salts, heavy metals and organic materials that are found in the exploitation of oil and material gas formations.
A freeze-thaw/evaporation purification process has been used to treat water produced in conjunction with oil and natural gas extraction. This water reportedly contains dissolved solids at a total dissolved solid (TDS) concentration of 12,800 mg/L. The reported xe2x80x9cnet result was an 80 percent reduction in the volume of water requiring disposal. Only 1612 [barrels] of the original produced water volume [of 8000 barrels] remained with a final TDS concentration of 44,900 mg/L; the remainder having been either evaporated or purified to a level of 1010 mg/L [or about 1010 ppm].xe2x80x9d Treating Produced Waters in the San Juan Basin with Freeze-Thaw/Evaporation Process, at  less than http://www.gri.org/pub/oldcontent/techn/e+p/gastips/fall97/treat.htm greater than , visited Jun. 16, 2000. This process reportedly operates in batch mode and when enough ice is accumulated over an elevated pipe framework, the ice is melted to recover purified water. See id. Dissolved solids in water treated according to this method are nonsettleable material. It would be desirable to provide a method and system for separating purified water from organic waste that contains settleable and nonsettleable material, such as organic waste produced in hog farms and other organic waste sources. This organic waste, in contrast with saline water and water associated with oil and gas production operations, is a more complex fluid because its composition includes setteable and nonsettleable materials such as suspended and dissolved solids, including fine solids of predominantly organic origin, various biomaterials and bio-related materials, various inorganic materials and their complexed and combined forms with the bio and bio-related materials, such materials being present in the complex organic waste in a variety of aggregation and phsyicochemical forms such as solution, suspension, and colloidal forms.
Still other methods have been reported for desalinating waters by freeze-thaw processes applied to aquifer waters. See, e.g., John E. Boysen, et al., Evaluation of the Natural Freeze-Thaw Process for the Desalination of Groundwater From the North Dakota Aquifer to Provide Water for Grand Forks, North Dakota, Water Treatment Technology Program Report No. 23, Water Treatment Engineering and Research Group, Technical Service Center, Bureau of Reclamation, U.S. Department of the Interior, September 1999.
Other water desalination processes rely on clathrate formation. See, e.g., Richard A. McCormack, et al., Clathrate Desalination Plant Preliminary Research Study, Water Treatment Technology Program Report No. 5, Water Treatment Engineering and Research Group, Technical Service Center, Bureau of Reclamation, U.S. Department of the Interior, June 1995. Still other methods to obtain purified water rely on distillation, filtration, and/or reverse osmosis. These processes require specialized facilities and typically require a high energy input.
Despite the plurality of methods for treating organic waste and for producing fertilizer and/or purified water, conventional methods leave unsolved problems. This is particularly the case regarding strategies that rely on encompassing and integrating organic waste treatment methods, fertilizer production processes for making fertilizer with desired environmental and agronomical properties, and/or separation of purified water from the waste. More specifically, there is a need for commercially successful organic waste treatment, fertilizer production and/or purified water recovery processes.
The composition of animal waste depends on both the kind of animal and the way the waste is handled. Poultry operations generally produce dry waste, with about 15%-25% moisture whereas hogs and cattle generate waste that is more liquid. In addition, water is typically used to flush hog and cattle waste out of barns and into storage facilities, thus producing a slurry that can be up to 97% liquid and it is typically stored either in earthen lagoons or in slurry tanks. In these conventional treatments, xe2x80x9cmany of the solids (including much of the phosphorous) settle into a sludge at the bottom. Most nitrogen remains dissolved in the water or volatilizes into the atmosphere. A farmer who utilizes the animal waste for nutrients pumps the liquid out for nutrients or irrigation, and may agitate the sludge at pumping time to capture the nutrients that otherwise would remain behind.xe2x80x9d Animal Waste Pollution in America: An Emerging National Problem, Environmental Risks of Livestock and Poultry Production, Report Compiled by the Minority Staff of the US Senate Committee on Agriculture, Nutrition, and Forestry for Sen. Tom Harkin, December 1997.
Most methods that rely on conventional lagoons do not clarify the effluent that carries the organic waste prior to its accumulation in the lagoon system. This practice leads to unnecessarily high loading of the lagoon system, thus requiring large conventional lagoons. Whereas some recently introduced lagoon treatments claim to reduce odors, these treatments essentially increase greenhouse gas emissions, such as carbon dioxide and ammonia gas emissions.
In anaerobic lagoons, one of the more common methods of hog manure treatment, organic matter in the waste is decomposed by bacteria. These lagoons are under increased criticism for offensive odor can result from incomplete decomposition and because of possible ground water contamination. Anaerobic lagoons also diminish nutrient value in the hog wastes through processes that include the loss during digestion of much of the nitrogen in the waste. Furthermore, conventional lagoon methods include the retention for long periods of time of big volumes of water that is meanwhile not used for productive purposes. To make these conditions worse, the activities that generate the organic waste that is conventionally treated in lagoons generally have a very high fresh water demand.
Currently, organic waste is largely treated and disposed of by relying on technology developed in the 1940""s for small scale operations, and integrated waste systems are nonexistent. In particular, most of the presently available waste treatment and disposal methodology relies on single unit operations which address a single problem or a very reduced number of problems. This approach cannot solve the variety of environmental, economical, operational, and technological problems that the multifaceted waste treatment and fertilizer production industry faces.
Another limitation faced by most conventional waste treatment methods is the inability to effectively treat large amounts of organic waste and produce purified re-usable water. This limitation becomes particularly relevant in a production framework in which large animal operations gain efficiency by raising a very large number of animals in controlled indoor environments which in turn produce enormous amounts of organic waste. See, for example, Warren Cohen, United States Deep In Manure, US News and World Report, Jan. 12, 1998, p. 46.
Modern farming operations must address the problems that are inherent to the confining of large numbers of animals in concentrated feeding operations. To this respect, it has been reported that more manure is produced in some areas of the US than can be safely applied to available crop land. See, for example, National Legislation Needed to Address Animal Waste Pollution, Senate Panel Told, BNA Environment Reporter, Vol. 28(49) (1998) pp. 2647-49, and Waste From Hog, Chicken Farms Growing at xe2x80x98Alarmingxe2x80x99 Rate, Group Says, BNA Environment Reporter, Vol. 28(48) (1998) pp. 2648-50. As noted above, these operations typically consume big volumes of water and they also generate huge volumes of waste water.
Sewage waste water treatment faces some of the same problems and raises similar concerns. Whereas the US has been regarded as a leader in sewage management, and sewage-treatment technology has been described as a success story in 20th-century US, it has been asserted that significant commercial advantages have been significantly lacking in the past few decades. Moreover, existing treatment methods have been characterized as facing a number of inherent problems that must be overcome to make further progress in the next century. William J. Jewell, Resource-Recovery Wastewater Treatment, American Scientist, Vol. 82 (1994) pp. 366-75.
Supply is a fundamental issue in fresh water resource management. It has been reported that water will xe2x80x9cbe a seriously scarce resource in the coming decades as we move from a population of 5 or 6 billion to 10 billion,xe2x80x9d USA Today, Jun. 5, 1996. This predicted scarcity is in contrast with the seemingly abundant supply of water in our planet, where at least 70% of its surface is covered by water. However, it is reported that only about 2.5% of all the world""s water is fresh, fit for human consumption, agriculture and industry. Furthermore, it is estimated that only about 0.3% of the total fresh water is usable for the world""s entire human and animal populations. Rising population, urbanization and economic growth have put major constraints on the availability of fresh water.
These concerns for the need and supply of fresh water have been manifested in a recent Report for Congress, which in a relevant part states that xe2x80x9c[g]rowing population and changing values are increasing demands on existing water supplies, resulting in water use conflicts throughout the country. These conflicts are particularly evident in the West, where population is expected to increase by 30% in the next 20-25 years and where urban needs often conflict with agricultural needs, as well as with increased demand for water for endangered species, recreation, and scenic enjoyment.xe2x80x9d Betsy A. Cody and H. Steven Hughes, Congressional Research Service. Report for Congress. RS20569: Water Resource Issues in the 106th Congress, updated Sep. 22, 2000,  less than http://www.cnie.org/nle/h2o-28.html greater than , visited Oct. 18, 2000.
Attempts in the industry to overcome the multifarious limitations that are inherent to single unit operations have failed to date because of the inability to implement them economically or because of operational and technical difficulties. This limited scope of the current waste treatment and disposal technology has lead to industry problems that have received intense scrutiny by the media. Therefore, an encompassing, integrated waste treatment system is a long felt, yet unsatisfied, need in agribusiness. The need for an encompassing and integrated waste treatment system has been expressed in a plurality of articles, statements on public health impacts and studies and regulations on animal feeding operations.
The EPA and legislators have been increasingly sensitive to the problems caused by current organic waste disposal practices and they have been focusing on the need to address such problems. In particular, the development of scientifically valid limits on land application of manure has been called, and the EPA has been reported as planning to revise the feedlot effluent limitations guidelines for poultry and swine by 2001, and for beef and dairy cattle by 2002. See Federal Role in Animal Waste Control Should Be Limited, House Panel Told, BNA Environment Reporter, Vol. 29(3) (1998) pp. 178-79; Draft Strategy for Animal Feeding Operations, EPA Memorandum, Mar. 4, 1998, and Compliance Assurance Implementation Plan For Concentrated Animal Feeding Operations, Office of Enforcement and Compliance Assurance, EPA, Mar. 5, 1998.
Acridity problems have also been increasingly addressed by legislators and government agencies. For example, following a recommendation from the Missouri Department of Natural Resources, the State of Missouri Air Conservation Commission reportedly agreed on Feb. 3, 1998, to form a task force to analyze odor pollution issues related to large hog and poultry farms in the state. See Task Force to Study Odor Issues Relating to Large Hog, Poultry Farms, in BNA Environment Reporter, Vol 28(40) (1998) p. 2134.
In addition to the focus on the problems that untreated organic waste discharge may cause, government strategies have also highlighted the need for developing new technological approaches for treating organic waste, pointing out in particular that the use of successful and innovative technological approaches should be encouraged and pursued. Draft of the Strategy for Addressing Environmental and Public Health Impacts From Animal Feeding Operations, EPA, March 1998, pp. 11-12.
Furthermore, recovery of purified water from the waste generated in organic waste sources for its use in agriculture, farms and livestock operations is a desirable goal because of the increasing fresh water scarcity and the big volume of water needed for such operations.
There is therefore a need in the art for an efficient, simple, economically viable method and system for converting organic waste into useful products such as fertilizers. There is also a need in the art for an efficient, simple, economically viable method and system for recovering purified water from organic waste, so that the purified water can be used in productive practices such as agriculture, farming and livestock operations.
More specifically, there is a need for processes and systems to separate purified water from organic waste so that a high percentage of the water from the organic waste is recovered in the form of fresh water that can be used in farm and agricultural applications, and such that these processes and systems satisfy the following conditions: (a) they are environmentally acceptable; (b) they do not rely on the use of toxic substances; (c) they do not require the incorporation into the process of extraneous substances to accomplish the separation of fresh water, these extraneous substances being exemplified by clathrate-forming substances and refrigerants; (d) they permit the production of low cost fresh water; (e) they do not rely on mechanically separated separation devices such as centrifuges, filters, drum crystallizers and crystallization rollers; (f) they do not rely for the separation of fresh water on power-operated thermal devices such as powered heat exchangers, refrigerators, vacuum freezers, and heaters; (g) they are simple to implement, compatible with and suitable for their incorporation into the organic waste treatment environment of organic waste sources such as hog farms; (h) other than equipment for fluid circulation and fluid flow control, they primarily rely on external climatic conditions and they are suited for their operation under exposed conditions; (i) they do not rely on subsequent treatments such as coagulation and/or filtration for the separation of fresh water, but instead they lead to the direct separation of fresh water upon subjecting the feed waste fluid to suitable freeze-thaw conditions that do not rely on multiple solid-liquid-vapor phase transformations; (j) the waste fluid itself in the processes and systems is separated into fresh water without having to resort to solid atomization, solid-state processing of crystallites of various compositions, freeze drying and/or vaporization; (k) they can easily be automated; they do not rely on land applications of residual waste products, such as waste stream; (m) they are suitable for effectively separating fresh water from complex organic waste fluid that includes setteable and nonsettleable materials such as suspended and dissolved solids, including fine solids of predominantly organic origin, various biomaterials and bio-related materials, various inorganic materials and their complexed and combined forms with the bio and bio-related materials, such materials being present in the complex organic waste in a variety of aggregation and phsyicochemical forms such as solution, suspension, and colloidal forms; (n) they are suitable for directly treating organic waste that has not been subjected to a conventional primary treatment, also known as a conventional lagoon treatment, upon organic waste production in a center such as a hog farm; and (o) they can effectively treat and separate fresh water from the enormous volume of physicochemically complex organic waste generated by large farms, such as hog farms holding a number of animals in a range as high as from 50000 to 100000 or more.
Each of the afore-mentioned elements of related art is hereby incorporated by reference in its entirety for the material disclosed therein.
The present invention has been developed in response to the present state of the art and, in particular, in response to problems and needs that have not been solved heretofore.
Methods and systems according to the present invention permit the separation of valuable substances from organic waste. These valuable substances include purified water and nutrients, such as fertilizers. Organic waste that is treated according to the present invention includes complex forms of waste, such as organic waste that comprises setteable and nonsettleable materials such as suspended and dissolved solids, including fine solids of predominantly organic origin, various biomaterials and bio-related materials, various inorganic materials and their complexed and combined forms with the bio and bio-related materials, such materials being present in the complex organic waste in a variety of aggregation and phsyicochemical forms such as solution, suspension, and colloidal forms.
Implementation of methods and systems according to the present invention includes controlled freeze/thaw processes. Evaporation is also included in some embodiments of the present invention. Embodiments of methods and systems according to the present invention provide a closed processing loop that requires no land application of waste. Waste constituent recovery according to embodiments of the present invention is envisaged to be at least 98%. Recovered constituents include highly soluble components such as potassium, sulfates, chlorides, and soluble organic material. Purified water recovery according to embodiments of the present invention provides up to about 66% of the total fresh water requirements of the farm that generates the organic waste from which the purified water is recovered.
The various controlled freeze/thaw operations according to the present invention include, but are not limited to, operations in a single spray field, and they also include processes that can be implemented in staged operations to increase the separation into purified water and brine fraction in other embodiments. Furthermore, the number of fractions separated in any given spray field according to the present invention includes, but is not limited to, purified water and one brine fraction, and also a number of fractions that comprise purified water and a plurality of brine fractions in other embodiments. Brine is subjected to various separations in staged operations according to the present invention.
Embodiments of the systems and methods according to the present invention permit the separation of purified water and/or nutrient materials from organic waste with low capital and operating costs, with relatively simple methodology that can easily be automated, providing near full recoveries of the valuable materials in the organic waste, eliminating the need for land applications of residual waste products, such as waste stream, and providing for water re-use as fresh water.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following specification and drawings, or may be learned by the practice of the invention as set forth hereinafter.